Measurement Time Duration Research Articles

Ability of RTK-Based GPS Measurement Method in High Accuracy Work in Geomatics Study

Abstract: Insfrastructure development require significant changes and transformation in Geomatics field for the upcoming decade. The use of new technology in Geomatics and surveying is essential and can be leveraged in many survey application that will help on building the nation towards a sustainable future. In the last 5 years, GNSS technology has been widely used and practiced to replace total station for survey work. Main factors that contributes to this busniness changes are the availability of much cheaper equipment with good technical capability in the market that helps surveyor to perform their work faster and more efficient. Global navigation satellite system services for accurate positioning has also rapidly increased and provide many option and solution for industry player or surveyor to choose. Combination of multiple global navigation satellite system providers such as GPS, GALILEO,GLONASS and BeiDOU has developed good satellite networks and increased numbers of available satellites for observation that improve absolute position accuracy. CHC i70 is among the best selling GNSS model on the market right now. The receiver can receive signal from GPS,GALILEO,GLONASS and BeiDOU simultaneously. This study will outline and focus on the capability of the RTK-Based method ( 30 second to 1 minute observation period) using CHC i70 instrument in high-precision measurement work. The research was done using the GPS calibration test site at Politeknik Sultan Haji Ahmad Shah (POLISAS) and was also practiced in the actual work for establishment of Temporary Bench Mark (TBM) along Jalan Melor to Ketereh, Kelantan. The result of the study found that RTK-Based method can meet the precision work that is permitted under 2cm accuracy. Studies show that the method of using RTK- Based is suitable for high precision work and improve the measurement time and work duration at field.
 
 Keywords : Beidou, Chc and RTK-Based GPS and PDOP

Influence of flicker noise and nonlinearity on the frequency spectrum of spin torque nano-oscillators

The correlation of phase fluctuations in any type of oscillator fundamentally defines its spectral shape. However, in nonlinear oscillators, such as spin torque nano-oscillators, the frequency spectrum can become particularly complex. This is specifically true when not only considering thermal but also colored 1/f flicker noise processes, which are crucial in the context of the oscillator’s long term stability. In this study, we address the frequency spectrum of spin torque oscillators in the regime of large-amplitude steady oscillations experimentally and as well theoretically. We particularly take both thermal and flicker noise into account. We perform a series of measurements of the phase noise and the spectrum on spin torque vortex oscillators, notably varying the measurement time duration. Furthermore, we develop the modelling of thermal and flicker noise in Thiele equation based simulations. We also derive the complete phase variance in the framework of the nonlinear auto-oscillator theory and deduce the actual frequency spectrum. We investigate its dependence on the measurement time duration and compare with the experimental results. Long term stability is important in several of the recent applicative developments of spin torque oscillators. This study brings some insights on how to better address this issue.

Stable and finely tunable optoelectronic oscillator based on stimulated Brillouin scattering and an electro-optic frequency shift.

We demonstrate a stable and finely tunable optoelectronic oscillator (OEO) based on stimulated Brillouin scattering. In the proposed scheme, the optical carrier in the OEO loop and the Brillouin pump light is generated by a single laser source, which guarantees the frequency stability of the output microwave signal from the OEO. Frequency tuning is achieved by varying the pump frequency via an electro-optic frequency shifter composed of a dual-parallel Mach-Zehnder modulator (DPMZM) and an electrical 90° hybrid. Through subtly varying the frequency of the low-frequency microwave signal applied to the DPMZM, a finely tunable high-frequency microwave signal can be obtained from the OEO. In the proof-of-concept experiment, the output frequency of the OEO is tuned from 10.645 GHz to 12.645 GHz with a tuning resolution of 10 MHz. The stable performance of the OEO is also achieved, where the maximum frequency and power drifts at 11.145 GHz are measured to be 6.25 kHz (i.e., ∼0.6ppm) and 0.77 dB in a measurement time duration of 1000 s, respectively. Through using broadband devices in the OEO architecture, the proposed scheme can generate stable and finely tunable microwave signals up to 40 GHz or even higher.

High-Throughput Satellite Characterization: Spot beam payload characterization of high-throughput satellites in a compact antenna test facility

An innovative measurement methodology is developed and successfully implemented for a spot beam antenna and payload characterization of high-throughput satellites (HTSs) in a compact antenna test facility (CATF). With the developed measurement methodology, total measurement time and measurement setup duration are reduced by more than 70% with respect to conventional measurement techniques. The proposed methodology is successfully implemented in multiple spacecraft (SC) of the Indian Space Research Organisation (ISRO).

Лидарное зондирование смеси молекул сероводорода и метана в атмосфере с летающей платформы

The back scattering Raman lidar equation for the gas mixture of the hydrogen sulfide and the methane molecules numerical solution results are presented at the hydrogen sulfide and methane molecules remote sensing in the atmospheric boundary layer with the concentration in the range of 1010 cm-3 … 1016 cm-3 from the flying platform at the heights up to 500 m in the synchronous photon counting lidar mode. It has been shown that the studied hydrogen sulfide molecules concentration at the level of 1,4 1011 cm-3 can be registered during measurement time duration of 10 s and the methane molecules concentration of 7,6 1015 cm-3 - during measurement time of 1 ms for such a lidar variant at the 405 nm laser radiation wavelength and the platform flight altitude up to 500 m.

Measurement Method of Temporal Attenuation by Human Body in Off‐the‐Shelf 60 GHz WLAN with HMM‐Based Transmission State Estimation

This paper discusses a measurement method of time‐variant attenuation of IEEE 802.11ad wireless LAN signals in the 60 GHz band induced by human blockage. The IEEE 802.11ad access point (AP) transmits frames intermittently, not continuously. Thus, to obtain the time‐varying signal attenuation, it is required to estimate the duration in which the AP transmitted signals. To estimate whether the AP transmitted signals or not at each sampling point, this paper applies a simple two‐state hidden Markov model. In addition, the validity of the model is tested based on Bayesian information criterion in order to prevent model overfitting and consequent invalid results. The measurement method is validated in that the distribution of the time duration in which the signal attenuates by 5 dB is consistent with the existing statistical model and the range of the measured time duration in which the signal attenuation decreases from 5 dB to 0 dB is similar to that in the previous report.

Limits to the precision of gradient sensing with spatial communication and temporal integration

Gradient sensing requires at least two measurements at different points in space. These measurements must then be communicated to a common location to be compared, which is unavoidably noisy. Although much is known about the limits of measurement precision by cells, the limits placed by the communication are not understood. Motivated by recent experiments, we derive the fundamental limits to the precision of gradient sensing in a multicellular system, accounting for communication and temporal integration. The gradient is estimated by comparing a "local" and a "global" molecular reporter of the external concentration, where the global reporter is exchanged between neighboring cells. Using the fluctuation-dissipation framework, we find, in contrast to the case when communication is ignored, that precision saturates with the number of cells independently of the measurement time duration, because communication establishes a maximum length scale over which sensory information can be reliably conveyed. Surprisingly, we also find that precision is improved if the local reporter is exchanged between cells as well, albeit more slowly than the global reporter. The reason is that whereas exchange of the local reporter weakens the comparison, it decreases the measurement noise. We term such a model "regional excitation-global inhibition." Our results demonstrate that fundamental sensing limits are necessarily sharpened when the need to communicate information is taken into account.

Identification of transfer functions from surge motion response of a semisubmersible platform using time-varying NARX model

Identification of transfer functions from surge motion response of a semisubmersible platform from model test data is presented in this paper. The identification is carried out by estimating the time-varying model coefficients of a time-varying NARX (TVNARX) model. The coefficients are estimated using proposed method, named artificial bee colony-based Kalman smoother (ABC-KS). System input–output data for identification process are wave height and surge motion from a scaled 1:100 model of a prototype semisubmersible. The applicability of proposed method is assessed numerically and experimentally under unidirectional long-crested random waves. The results show that the linear and quadratic frequency response functions as well as the wave and low frequency responses of a semisubmersible platform can be well identified either in time or frequency domains. The evolution of the nonlinear wave-structure interactions also can be revealed with respect to measured time duration.

A new concept of the contraction–extension property of the left ventricular myocardium

ObjectivesUsing newly developed ultrasonic technology, we attempted to disclose the characteristics of the left ventricular (LV) contraction–extension (C–E) property, which has an important relationship to LV function. MethodsStrain rate (SR) distribution within the posterior wall and interventricular septum was microscopically measured with a high accuracy of 821μm in spatial resolution by using the phase difference tracking method. The subjects were 10 healthy men (aged 30–50 years). ResultsThe time course of the SR distribution disclosed the characteristic C–E property, i.e. the contraction started from the apex and propagated toward the base on one hand, and from the epicardial side toward the endocardial side on the other hand. Therefore, the contraction of one area and the extension of another area simultaneously appeared through nearly the whole cardiac cycle, with the contracting part positively extending the latter part and vice versa. The time course of these propagations gave rise to the peristalsis and the bellows action of the LV wall, and both contributed to effective LV function.The LV contraction started coinciding in time with the P wave of the electrocardiogram, and the cardiac cycle was composed of 4 phases, including 2 types of transitional phase, as well as the ejection phase and slow filling phase. The sum of the measurement time duration of either the contraction or the extension process occupied nearly equal duration in normal conditions. ConclusionThe newly developed ultrasonic technology revealed that the SR distribution was important in evaluating the C–E property of the LV myocardium. The harmonious succession of the 4 cardiac phases newly identified seemed to be helpful in understanding the mechanism to keep long-lasting pump function of the LV.

Homotopy Iteration Algorithm for Crack Parameters Identification with Composite Element Method

An approach based on homotopy iteration algorithm is proposed to identify the crack parameters in beam structures. In the forward problem, a fully open crack model with the composite element method is employed for the vibration analysis. The dynamic responses of the cracked beam in time domain are obtained from the Newmark direct integration method. In the inverse analysis, an identification approach based on homotopy iteration algorithm is studied to identify the location and the depth of a cracked beam. The identification equation is derived by minimizing the error between the calculated acceleration response and the simulated measured one. Newton iterative method with the homotopy equation is employed to track the correct path and improve the convergence of the crack parameters. Two numerical examples are conducted to illustrate the correctness and efficiency of the proposed method. And the effects of the influencing parameters, such as measurement time duration, measurement points, division of the homotopy parameter and measurement noise, are studied.

Structural Condition Assessment from White Noise Excitation and Covariance of Covariance Matrix

The sensitivity of covariance of covariancematrix with respect to a local stiffness change in the structural system is derived analytically based on the auto/cross-correlation function of the acceleration response, and the original covariance of covariance formula is improved for use with any number of selected structure modes. This paper presents the approach using the improved covariance of covariance matrix of acceleration response for structural condition assessment under white noise support excitation. A simply supported 31 bar plane truss with and without 10% measurement noise is studied numerically. Results show that the sensitivity approach with the covariance of covariance matrix is accurate, and when including the finite impulse response forward and backward filtering technique, themethod would be suitable for industrial application. The covariance of covariancemethod is shown to be insensitive to measurement noise when the measurement time duration is sufficiently long.

Identification of both structural damages in bridge deck and vehicular parameters using measured dynamic responses

A method to identify both damages in bridge and the vehicular parameters from the structural dynamic responses is presented. A dynamic response sensitivity-based finite element model updating approach is used to identify both the structural damages and the vehicular parameters. The solution is obtained iteratively with the penalty function method with regularization from the measured dynamic responses. The effects of measurement noise, different vehicle models, measurement time duration and modeling error on the identification results are investigated in the numerical simulation. Studies in this paper indicate that the proposed method is efficient and robust for both damage and parameter identification.

Optimal measurement scheduling for state estimation

We consider the problem of optimal allocation of measurement resources, when: (1) the total measurement budget and time duration of measurements are fixed, and (2) the cost of an individual measurement varies inversely with the (controllable) measurement accuracy. The objective is to determine the time-distribution of measurement variances that minimizes a measure of error in estimating a discrete-time, vector stochastic process with known auto-correlation matrix using a linear estimator. The metric of estimation error is the trace of weighted sum of estimation error covariance matrices at various time indices. We show that this problem reduces to a nonlinear optimization problem with linear equality and inequality constraints. The solution to this problem is obtained via a variation of the projected Newton method. For the special case when the vector stochastic process is the state of a linear, finite-dimensional stochastic system, the problem reduces to the solution of a nonlinear optimal control problem. In this case, the gradient and Hessian with respect to the measurement costs are obtained via the solution of a two-point boundary value problem and the resulting optimization problem is solved via a variation of the projected Newton method. The proposed method is illustrated using four examples. >